1. Field of the Invention
The present invention relates to method and apparatus for image processing and, more particularly, to the claimed method and apparatus for image processing capable of high speed processing.
2. Description of the Related Art
An image processing apparatus or a program executing an error diffusion process has been known.
FIG. 15 is a block diagram representing a configuration of a conventional image processing apparatus employing the error diffusion method.
Referring to the figure, the image processing apparatus includes an input unit 501 successively receiving as inputs image signals (input values) representing density of respective pixels; a subtractor 503 reading an error value corresponding to a pixel of interest from an error memory 513 and subtracting the error value from the input value; a thresholding unit 507 thresholding, with a prescribed threshold value, an output (modified input) of subtractor 503; an output unit 509 outputting the result of thresholding (for example, the value 0/1); a subtractor 511 subtracting the output of subtractor 503 from the output of thresholding unit 507; and the error memory 513 distributing the output of subtractor 511 as an error to surrounding pixels and stores.
By the image processing apparatus configured as described above, an error in pixel density resulting from gradation reducing process is diffused. Therefore, it becomes possible to reduce gradations of an image as an object of processing, while maintaining the density of the image as a whole.
The conventional image processing apparatus, however, has a problem that the speed of processing is low.